1. Field of the Invention
The present invention relates to designs and methods for reducing the effects of drag forces present during the use of a golf club head that conform to the U.S.G.A. Rules of Golf.
2. Description of the Related Art
Golf club designs, and driver designs in particular, have recently trended to include characteristics intended to increase the club's inertia values to help off-center hits go farther and straighter. Driver designs have also recently included larger faces, which may help the driver deliver better feeling shots as well as shots that have higher ball speeds if hit away from the face center. These recent trends can, however, be detrimental to the driver's performance due to the head speed reductions that these design features introduce due to the larger geometries. In fact, a wood or metal wood club head behaves aerodynamically as a bluff body during downswing, exhibiting large separated flow regions and generating significant drag forces, which reduce head speed and can negatively affect control of the club during a swing.
Numerous approaches to reducing the drag of woods, including metal wood, club heads have been proposed. The majority of these approaches involve modification or addition of features to the body of the club, exclusive of the striking surface or face. These include changes to the crown, sole, ribbon, toe, and heel portions of the club, referred to herein as “body only” modifications. Examples of such methods include the embodiments disclosed in U.S. Pat. No. 6,942,581 to Kim et al., U.S. Pat. No. 6,773,359 to Lee, U.S. Pat. No. 6,074,308 to Domas, U.S. Pat. No. 5,980,394 to Domas, U.S. Pat. No. 5,954,595 to Antonious, U.S. Pat. No. 5,735,754 to Antonious, U.S. Pat. No. 5,700,208 to Nelms, U.S. Pat. No. 5,511,786 to Antonious, U.S. Pat. No. 5,203,565 to Murray et al., U.S. Pat. No. 5,221,086 to Antonious, U.S. Pat. No. 5,913,810 to Antonious, U.S. Pat. No. 5,120,061 to Tsuchida et al., U.S. Pat. No. 4,850,593 to Nelson, and U.S. Pat. No. 4,444,392 to Duclos. While this type of approach may maintain the impact properties of the face, the aerodynamic benefits of these designs treatments are greatly reduced by the large scale flow separation created by traditional face geometry. In addition, many of these designs violate the “plain in shape” requirements of the U.S.G.A. Rules of Golf as described in Rule 4a, Appendix II.
Several other prior art designs include significant geometric changes to both the body and the striking surface. Examples of these designs include the embodiments disclosed in U.S. Pat. No. 5,997,413 to Wood, U.S. Pat. No. 5,803,830 to Austin et al., U.S. Pat. No. 5,674,136 to Gorse, U.S. Pat. No. 5,318,297 to Davis et al., U.S. Pat. No. 5,271,622 to Rogerson, U.S. Pat. No. 4,900,029 to Sinclair, U.S. Pat. No. 4,809,982 to Kobayashi, and U.S. Pat. No. 4,431,192 to Stuff, Jr. These designs exhibit the same problems as the “body only” modification approaches. Furthermore, modification of these clubs' face geometry also tends to yield poorer impact performance.
Some prior art designs are characterized by through-holes extending from the face. Examples of this design characteristic are shown in the embodiments disclosed in U.S. Pat. No. 6,824,474 to Thill, U.S. Pat. No. 6,319,148 to Tom, U.S. Pat. No. 6,165,080 to Salisbury, U.S. Pat. No. 6,027,414 to Koebler, U.S. Pat. No. 5,944,614 to Yoon, U.S. Pat. No. 5,807,187 to Hamm, U.S. Pat. No. 5,681,227 to Sayrizi, U.S. Pat. No. 5,524,890 to Kim et al., U.S. Pat. No. 5,158,296 to Lee, and U.S. Pat. No. 5,054,784 to Collins. Though this technique can provide aerodynamic benefits via wake ventilation, it also fails to conform to the Rules of Golf and can adversely affect impact performance. A similar approach utilizes grooves or channels that extend to the face or striking surface, examples of which are shown in the embodiments disclosed in U.S. Pat. No. 5,004,241 to Antonious, U.S. Pat. No. 4,930,783 to Antonious, U.S. Pat. No. 4,828,265 to Antonious, and U.S. Pat. No. 4,065,133 to Gordos. These approaches can also have an adverse effect on impact performance, and are also nonconforming under the Rules of Golf plain in shape” requirement.
A few prior art approaches attempt to alter the face shape, including those disclosed in U.S. Pat. No. 5,944,620 to Elmer, U.S. Pat. No. 5,961,397 to Lu et al., U.S. Pat. No. 5,747,666 to Lovett, and U.S. Pat. No. 3,976,299 to Lawrence et al. The problem with these designs, however, is that their structure can negatively affect impact performance of the face. For instance, reducing or eliminating the high center region of the face removes a common hit location, thus reducing the forgiveness and effectiveness of the club.
It is clear from the references discussed above that the prior art fails to provide golf club designs that efficiently reduce drag forces, enable the golf club to be swung faster along its path, and improve the impact event with the golf ball.